The present invention relates to methods of forming poly(aryl ether sulfone)s and articles therefrom, and more specifically to methods of forming poly(aryl ether sulfone)s by melt polymerization.
Poly(aryl ether sulfone)s are highly-utilized, tough, ductile thermoplastics that have the advantage of solubility in organic solvents and are therefore processable. In addition, they can be mixed with other monomers in order to form random copolymers, a technique that often improves the mechanical properties of the poly(aryl ether sulfone) while maintaining its solubility. Due to their resistance to oxidation and hydrolysis, they are produced for water purification membranes, acidic solid support resins, as well as medical devices. In industry, poly(aryl ether sulfone)s are used for a wide range of applications including composites, plumbing and electronics. Because poly(aryl ether sulfone)s contain polar sulfone functional groups, they can be mixed with dyes to produce colored plastics.
Poly(aryl ether sulfone)s have been prepared using stoichiometric quantities of potassium carbonate (K2CO3), a mild base, bisPhenol A (BPA) monomer, and a bis-haloaryl sulfone monomer (Scheme 1).

High reaction temperatures (>170° C.) are needed in order to remove the byproduct, water, from the reaction mixture. Due to high demand for these types of polymers for industrial processes, milder methods of synthesizing a poly(aryl ether sulfone) would be of high value. Efforts to improve the reactivity of aryl halides for the synthesis of poly(aryl ether sulfone)s include placing an activating group at the ortho-position of the aryl ring of the sulfone monomer in order to influence the formation of the Meisenheimer complex, the reactive intermediate in the formation of the aryl ether linkage (Scheme 1).
Another approach utilized a catalytic quantity of a metal fluoride (e.g., cesium fluoride) for activation of bis-TMS protected bis-Phenol A monomer, which resulted in addition of BPA to a di-haloaryl sulfone monomer. The reaction was successful without solvent, and effectively showed that fluoride was effective in activating the silicon group for nucleophilic transfer and formation of the Meisenheimer complex. The metal is a potential contaminant, and therefore a drawback in the large scale production of poly(aryl ether sulfone)s.
Another problem associated with the above methods of preparing poly(aryl ether sulfone)s is chemical “backbiting” of the polymer chain during chain growth, which leads to mixtures of cyclic and linear polymers of various molecular weights. In polycondensation reactions, the most probable polydispersity index (PDI) is about 2.0. A smaller PDI would be desirable.
Methods of producing more narrowly dispersed poly(aryl ether sulfone)s are needed, which do not employ a metal catalyst and do not produce a cyclic byproduct.